Living with the Mossberg 930 (Particularly the SPX Version)
In my mind the Mossberg 930 shotguns are the sleeper of the shotgun world. While some of the early ones had issues, the current production ones are well made and very reliable, and have less recoil than the recoil operated Benneli, and HK equivalents. Like all firearms these days there are some tips and tricks to make them even better. While some of the early ones had some issues, the current production is excellent. Have close to 600 round through mine with zero problems.
Just a note. If you already have a 930 SPX there's no reason to ditch it to get a 940. What Mossberg has effectively done is to install an adjustable standard butt stock (that they said couldn't be done with the 930 (Ha! Ha! we know differently - see below), added the equivalent of the OR3GUN improved spacer tube, and deleted the rail and rear sight. With the tips and tricks here you effectively turn the 930 into a 940, and you'll have a rail and iron sights that don't come with the 940. With the 940 being the cool "new thing" you can frequently pick up one of those "old model" 930s for $600 - $700. A friend recently got a NIB 930SPX for $650.
Owner's Manual Errata
Click here to view the errata page.
Parts Schematic
Click here for a parts schematic and exploded view. The numbers in parenthesis below are the callouts on this exploded view. Note that the numbers are different on this drawing than in theowner's manual, and are used below..
Checks
Return Spring (#63) – Inspect both ends of spring to ensure cut ends are not rubbing the inside of the return spring tube (#50). Reshape if necessary to ensure no contact. Lightly lube spring and inside of tube. Note: threads on the tube are 5/8-32. One interesting fix is to insert a ½ inch stainless steel washer between the return spring and the return spring plunger (#48) as there have been reports of the end of the spring damaging the plunger. You can stick the washer to the plunger with a drop of glue to hold it in place during assembly.
Safety (#55).-- Ensure smooth movement of safety. Can polish bottom, and relieve the edges of detent holes in the metal plate under the safety and polish. Lightly lube bottom of safety and the sides of the notch in the receiver the safety block rides in. Consider one of the numerous after market metal ones. To lighten safety movement even more, remove ball and spring and cut the spring so the end is just below flush with the top of its hole. Reinsert spring with the cut end down. A little light grease will hold ball and spring in place for reassembly
Trigger Assembly ( #76) – Lightly polish hammer face and other surfaces that rub on other parts. You can use a fine wire wheel in the sear notch to remove any tiny burrs. If you feel the pull is too heavy there is a lighter trigger spring available that will reduce the pull weight by about 2 pounds. About $13.
https://www.mcarbo.com/mossberg-930-/-935-trigger-spring-kit.aspx
Light grease on hammer face and other contact points (obvious to anyone with brains). Clean and relube assembly after heavy use. (DUH!)
Barrel (#2) – The bore, while fairly smooth can be improved. Polish the bore with KG2 Bore Polish using a bore mop wrapped in a patch on a cleaning rod. Can spin with a drill. Keep gas ports up. After spinning patch with a drill, do some manual back and forth swipes with a fresh patch and KG2. When shinny, clean normally. Will greatly reduce fouling
Magazine tube (#26) and extension (Not numbered) – Current tubes should be very smooth inside. If not, use a 10 ga bore brush and a cleaning rod on a drill. Wipe out, and very lightly lube interior, and then wipe dry. Replace factory follower with GG&G (#1440) or other aftermarket machined follower. Keep outside of magazine tube clean and free of fouling, and lightly lube and wipe dry to ensure gas piston (#18) moves freely.
Keep inside of spacer tube clean and lightly lubed. If you shoot a lot of light loads you might consider one of the OR3GUN blue perforated ones, or the gray perforated one for standard/heavy loads. There are some sources who call the perforated extension tube a "marine tube" based on the premise that in wet environments water can drain out faster. This has not been confirmed and probably not an issue in the southwest.
Both the blue perforated lightened and and a gray perforated standard weight spacers, with an improved design, are available from
http://www.or3gun.com/OR3GUN/about_or3gun_marine.htm
Gas piston (#18) – Ensure piston and rings are clean , free from fouling and lightly lubed. Do the same with the gas cylinder on the barrel The two gas port holes can be cleaned with a pipe cleaner. Set rings so the splits are opposite each other. Consider replacing with the Pro Series, nitrided finished, piston assembly (16801BN) . Much slicker and easier to clean.
Bolt release (part of #62) – For easier operation consider replacing the factory one with the GG&G unit which has a larger area. About $55. Available from
https://www.primaryarms.com/gg-g-mossberg-930-tactical-bolt-release-pad-tactical-black-ggg-1756
or
https://www.opticsplanet.com/gg-g-mossberg-930-tactical-bolt-release-pad.html (free S&H)
Stock Shortening
The big problem with the 930s is their extremely long (14 inch) LOP which make gun handling (especially the SPX) difficult with heavy clothing or load bearing equipment. Mossberg officially denies it is possible to shorten the stock, but there is an after market option available in the form of Mesa Tactical's Urbino pistol grip stock. They seem to be quite popular but they require a little work for installation. In fact, it IS possible to shorten the factory non-pistol grip stock, but it takes some real work. See link below.
See the stock shortening page with more details by clicking here.
Side Saddle Warning
Many people carry spare ammo in a side saddle attached to the side of the receiver. Be aware that you can bind the action if the screws are too tight, causing short stroking and failure to lock open on the last shot.. Before mounting note the ease of the action and then do not tighten the mounting screws more than just barely tight and check for interference with the action. The side saddle will usually have to be a little loose on the gun for it to function properly. You can secure the mounting screws with a dab of Blue Loctite when assembling. This applies to all semi autos.
A probably better option if you want on-gun ammo on a semi-auto is the Esstac soft ammunition strips which attach to the receiver with industrial strength Velcro. They are very popular and are available 4, 5, 6, and 7 rd configuration, and numerous colors. The length in inches of the strips is about the number of rounds in the strip. The 6 round strips fit nicely on the 930. Before mounting the "loop" (soft fuzzy piece) velcro strip to the receiver you should degrease the side of the receiver. You will need to trim the piece to fit both length wise and top to bottom, as well as punch a hole in it for the forward receiver pin so you can remove the trigger assembly. Additional “strips” can be carried in M16 30rd magazine pouches. Note that the loops are VERY snug and you'll have to work to get the rounds in the loops. Best done off the gun.
It is possible to use one of the conventional side saddles by using industrial strength Velco like the Esstac uses by putting the hook strip on the back of the mounting plate. Appropriate Velcro is available on Amazon.
https://amazon.com/gp/product/B08C6PMY9X/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1
Getting That *#$#@! Magazine Spring Back in the Tube
If you've ever struggled to get the long magazine spring back in the tube and then get the extension tube back on, here's a tip that will help.
Cut a piece of 5/8 inch OD PVC tubing about 2 feet long and round and smooth the ends. Then locate the little white plastic plug that went flying when you removed the extension tube. Slip the PVC tube inside of the magazine spring and carefully work the spring fully into the magazine tube. Holding the spring in place and remove the PVC tube. Place the plastic plug carefully into the spring and the slide the magazine extension tube over the end of the magazine tube. Hold it tight as the spring will snap up into the extension tube. Screw the extension tightly into place. It may help if you have a helper the first time you try this.
Unloading Tip
Need to empty the magazine tube? With the bolt forward put the safety on. (Duh!) Turn the 930 so the elevator is facing up and fully depress it. While holding it down press the bolt release and the magazine tube will dump any rounds in it into you hand. (You might have to pick up some rounds from the floor if you're not careful.). Then clear the chamber.
Failure To Feed
Some 930s, particularly early ones had an occasional problem feeding from a full magazine tube when working the bolt on an empty chamber. The issue was caused by the tip of the shell stop assembly (#62) having sharp edges on its tip. The fix is to polish the tip of the shell stop. Don't remove metal, just remove burrs and sharp edges. There are several videos of this process on YouTube. Search on "Mossberg 930 Magazine Feed Problem." None of the 930s in my area have had this issue but if you have the firearm disassemble you might want to check this out just in case.
Spare Parts
These should cover most problems or lost parts.) See the Mossberg Store. https://www.mossberg.com/parts-and-accessories/
Note: When ordering parts from Mossberg, call them rather than using the online store. Shipping is much less that way. 800-363-3555
Miscellaneous
Cleaning
How and where you clean and lube is more important than the brand of products you use. The following are highly recommended though.
Some folks brag about never cleaning their guns which is idiotic. You may get away with it in "gun games" but failures in real life can be fatal. Just remember that if you take care of your firearm, it will take care of you. Since cleaning and lubrication are well covered elsewhere I won't reinvent the wheel here. Just remember to clean the barrel with the gas port UP.
2¾ inch slugs in a 3 inch chamber
When not generally a major problem there does seem to be a reoccurring issue when using 2¾ inch slugs in a 3 inch chamber. (This applies to all shotguns.) Because of the unsupported ¼ inch jump between the end of the case and the beginning of the rather short (.4172 inches) forcing cone when using 2¾ inch slugs, especially Brenekes, slugs tend to shave lead in the chamber resulting in lead shavings in the action. While chamber drawing do not show a lip at the beginning of the forcing cone there usually is a slight one. This can be mitigated quite a bit by cleaning up and lengthening the forcing cone using a long forcing cone reamer.
An article on the process is available at https://rifleshooter.com/2013/02/extended-shotgun-forcing-cone/ or you can click here for an article on using a forcing cone reamer.
Please email comments or questions to Fr. Frog by clicking here.
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Disclaimer
As far as I know all the
information presented above is correct and I have attempted to ensure that it
is. Everything above worked fine for me, but your mileage may vary. I am not
responsible for any errors, omissions, or damages resulting from
the use or misuse of this information, nor for you doing something stupid with
it. (Don't you hate these disclaimers? So do I, but there are people out there
who refuse to be responsible for their own actions and who will sue anybody to
make a buck.)
Updated 2023-05-17 @ 2030